So im rigging my skis, and cant help hut wonder why do they suggest a 8-20 degree (depending on the publication) nose down on the front safety cable? I hear “its for drifts while taxiing” but its there for it the bungee gives- why would i want my ski tip pointed down to land if a bungee broke?

Im not challenging it, just cant figure out why...

If id ever loose a bungee ya just three point land and hope it doesn't catch and dig in?

You have to allow for quite a bit movement of the ski, before it "bottoms" out the cable. It's a compromise, but you definitely do not want to cable rig with the ski level, unless you will fly perfectly flat conditions all the time! I'd suggest you go with what others have figured out before you, don't re-invent the wheel, or ski

First, what “flavor” of skis are you dealing with?

Second, that solid forward cable is technically a “limit” cable. The bungees or springs are there to position and keep the nose of the skis UP for both “normal” ops and in the event that forward limit cable were to break, that spring or bungee is the only thing keeping that ski tip from going down.....and THAT is the beginning of a bad day at Black Rock.

The forward limit cable has to be long enough to allow the ski tips to pitch nose down far enough to slide over drifts, etc. I’d keep the nose down limit to the minimum specified, personally. What the manufacturer is limiting is the ability of the ski to rotate nose down, and go inverted in the event your bungee/spring were to break. On the other hand, if the ski isn't capable of nosing down some as it slides over a drift or obstacle during taxi, the heels of the skis are going to dig in, and you'll get stuck. Think about a track, moving over uneven ground. there's some up/down going on there, as the track moves to conform to the surface irregularities. Same for a ski, remember, they're pretty long.

Finally, I much prefer springs to bungees these days. The bungee materials made these days dont seem to hold their tension as well as the old ones did. I flew a Husky with bungees up front once, and when you nosed down slightly in flight to descend, those skis would go over to the limits: CLUNK, CLUNK. Which unnerved me, though I’d carefully inspected those limit cables. I suggested to maintenance that they either install springs or beefier bungees. New bungees made the difference.

The other angle that’s important is the angle of the skis in flight, as determined by the AFT limit cables. I like that as close to zero as manufacturer permits, and mechanic is willing to set. Cruise speed is dependent to a degree by this angle.

MTV

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I thought the same thing when I rigged my skis last year. But taxi around in less than perfect snow and you’ll see why they are rigged the way they are

I went through the same thing last year, installing skis for the first time. I did find a rig specific diagram with measurements for my plane and skis through the type club. Might be a resource like that out there for you that would tighten your range a bit. On the spring instead of bungee use, MTV, I need to replace my bungees, where would one find springs?

Pete

mtv wrote:First, what “flavor” of skis are you dealing with?

Second, that solid forward cable is technically a “limit” cable. The bungees or springs are there to position and keep the nose of the skis UP for both “normal” ops and in the event that forward limit cable were to break, that spring or bungee is the only thing keeping that ski tip from going down.....and THAT is the beginning of a bad day at Black Rock.

The forward limit cable has to be long enough to allow the ski tips to pitch nose down far enough to slide over drifts, etc. I’d keep the nose down limit to the minimum specified, personally. What the manufacturer is limiting is the ability of the ski to rotate nose down, and go inverted in the event your bungee/spring were to break. On the other hand, if the ski isn't capable of nosing down some as it slides over a drift or obstacle during taxi, the heels of the skis are going to dig in, and you'll get stuck. Think about a track, moving over uneven ground. there's some up/down going on there, as the track moves to conform to the surface irregularities. Same for a ski, remember, they're pretty long.

Finally, I much prefer springs to bungees these days. The bungee materials made these days dont seem to hold their tension as well as the old ones did. I flew a Husky with bungees up front once, and when you nosed down slightly in flight to descend, those skis would go over to the limits: CLUNK, CLUNK. Which unnerved me, though I’d carefully inspected those limit cables. I suggested to maintenance that they either install springs or beefier bungees. New bungees made the difference.

The other angle that’s important is the angle of the skis in flight, as determined by the AFT limit cables. I like that as close to zero as manufacturer permits, and mechanic is willing to set. Cruise speed is dependent to a degree by this angle.

MTV

Mine are Federal 1500s circa 1946.... So I have followed the old federal paperwork and the FAA AC guidlines and triangulated between the two...

I bought brand new bungees from wipaire last year (never got em mounted last year) so I'll probably roll with them and do the spring next time they need attention.

Being I'm new to it, and fly a low hp plane (1947 Cessna 140) I'll stick to pretty benign conditions for now... So primarily the frozen lakes, local grass strips and such...

Huckster79 wrote:

mtv wrote:First, what “flavor” of skis are you dealing with?

Second, that solid forward cable is technically a “limit” cable. The bungees or springs are there to position and keep the nose of the skis UP for both “normal” ops and in the event that forward limit cable were to break, that spring or bungee is the only thing keeping that ski tip from going down.....and THAT is the beginning of a bad day at Black Rock.

The forward limit cable has to be long enough to allow the ski tips to pitch nose down far enough to slide over drifts, etc. I’d keep the nose down limit to the minimum specified, personally. What the manufacturer is limiting is the ability of the ski to rotate nose down, and go inverted in the event your bungee/spring were to break. On the other hand, if the ski isn't capable of nosing down some as it slides over a drift or obstacle during taxi, the heels of the skis are going to dig in, and you'll get stuck. Think about a track, moving over uneven ground. there's some up/down going on there, as the track moves to conform to the surface irregularities. Same for a ski, remember, they're pretty long.

Finally, I much prefer springs to bungees these days. The bungee materials made these days dont seem to hold their tension as well as the old ones did. I flew a Husky with bungees up front once, and when you nosed down slightly in flight to descend, those skis would go over to the limits: CLUNK, CLUNK. Which unnerved me, though I’d carefully inspected those limit cables. I suggested to maintenance that they either install springs or beefier bungees. New bungees made the difference.

The other angle that’s important is the angle of the skis in flight, as determined by the AFT limit cables. I like that as close to zero as manufacturer permits, and mechanic is willing to set. Cruise speed is dependent to a degree by this angle.

MTV

Mine are Federal 1500s circa 1946.... So I have followed the old federal paperwork and the FAA AC guidlines and triangulated between the two...

I bought brand new bungees from wipaire last year (never got em mounted last year) so I'll probably roll with them and do the spring next time they need attention.

Being I'm new to it, and fly a low hp plane (1947 Cessna 140) I'll stick to pretty benign conditions for now... So primarily the frozen lakes, local grass strips and such...

Hey, it'll be fun.....take a shovel.

MTV

I think bungees get somewhat of a bad rap. No hangar, UV damaged, too small, yeah I could see that being a problem. I replaced my Datum bungees last year, after 10 years (hangared AND when parked, a block under the ski tip to unload the bungee) and they were still like new. I pull tested them against the new, and they seemed to exhibit identical elasticity. Steel springs can get worn out also.....and in some ways I like the multiplicity of the bungee, lot's of rubber cords, compared to a single point of failure with a spring? Just the word "bungee" sounds half ass, I try and use "shock cord" whenever possible.

I hung the old bungees on the shop wall, figuring they would come in handy for something.....2 months later one of my crane's mount brackets, for storing the outrigger pad shoes when on the road, fatigued and broke off, and the $650.00 aluminum shoe fell off somewhere between Challis and Mackay ID. I chose to not re-weld the original bracket, as it was the most vulnerable to damage due to it's most rearward location, but instead now just slide it up on the truck bed. No sideboards there though (have to leave room for the operator cab rotation), and as I puzzled over how to secure it, I remembered my old bungee! Works perfect, quick and easy, and very secure, a steel spring would work also I guess But I like a little bit of the plane on the crane.

courierguy wrote:I think bungees get somewhat of a bad rap. No hangar, UV damaged, too small, yeah I could see that being a problem. I replaced my Datum bungees last year, after 10 years (hangared AND when parked, a block under the ski tip to unload the bungee) and they were still like new. I pull tested them against the new, and they seemed to exhibit identical elasticity. Steel springs can get worn out also.....and in some ways I like the multiplicity of the bungee, lot's of rubber cords, compared to a single point of failure with a spring? Just the word "bungee" sounds half ass, I try and use "shock cord" whenever possible.

I hung the old bungees on the shop wall, figuring they would come in handy for something.....2 months later one of my crane's mount brackets, for storing the outrigger pad shoes when on the road, fatigued and broke off, and the $650.00 aluminum shoe fell off somewhere between Challis and Mackay ID. I chose to not re-weld the original bracket, as it was the most vulnerable to damage due to it's most rearward location, but instead now just slide it up on the truck bed. No sideboards there though (have to leave room for the operator cab rotation), and as I puzzled over how to secure it, I remembered my old bungee! Works perfect, quick and easy, and very secure, a steel spring would work also I guess But I like a little bit of the plane on the crane.

Bungees work fine till they don't. Like anything else, I guess. The issue I've seen in the last fifteen years or so is the quality and durability of bungee material doesn't seem as consistent, and the life span has shortened noticeably. Used to was, we had bungees on skis that were 20 years old. Not a great idea, but the dang things were still tough as hell. Sometime in the last 25 or 30 years, bungees tend to lose their "rebound" sooner. As long as you change them periodically, likely no issue.

I had a pair of old bungees on a Super Cub stretch out and refuse to come back in cold weather. I had landed, the bungees were in their "normal" nose up position, as dictated by the bungees....but after putting the tail down and parking the bungees stretched out some....almost to the forward limit cables. Temps were low, ~ minus 30 or so F. Bungees lost all their elasticity, and were done. In other words, the noses of the skis stayed down...... Because the snow was crusted, I was able to get airborne, but now I had toes of skis well down......lots of drag and nose down pitch. Trim all the way back, and lots of back pressure got me home, but wasn't a fun flight. Couldn't find in the plane's log books where the bungees had been changed last.

MTV

like a little bit of the plane on the crane.

Some plane on the crane on the plain!

Here’s some plane on the crane on the range for you!

Yes. The Hurricane is the real deal.

Great pic! Looks like a 60 or 80 ton Manitex?

The untold story about the picture I posted of my rig in front of that range, is that all four of my stabilizer pads are still there! I had driven 2.5 hours that day, stopped to take the picture as just the day before I was screwing around the same area in the plane, then drove another 30 miles to the jobsite and THEN found I was missing a pad. For all I knew at the time, I could have lost it anywhere along the drive, it wasn't until the next day that I looked at the picture and saw the pad (right rear) was still there! That narrowed my search area down tremendously, to the last 30 miles, so I drove up in my car, couldn't find it, then flew up a few days later, no dice. Put up reward signs in the area, no luck. Ordered and received the new one, and 2 days later got a call, someone had found the old one! I flew back up to get it, had the $250.00 reward money in hand, and the guy refused to accept it, it almost got ugly when I insisted, but he wouldn't budge, so I told him OK be that way, and flew home. Now, I have a spare pad, which means I'll never loose one again of course.

45 ton Manitex. 96’ boom. 32’-49’ foldaway offset jib. Two winches. 2007 Freightliner. 550 C15 Acero. 18 spd. auto shift so I could talk on the phone while I eat a sandwich and not have to hold the gear shift too! I seldom drive it anymore.

All that crane, and can still scale a 44,000 lb. payload! 137,000 lb. licensed GVW.

Lost more than one aluminium float in my day also. It happens.